docs: def _total_mask(self):
          """
          Combination of the _segment_mask, _input_mask, and _data_mask.
  
          This mask is applied to ``data``, ``error``, and ``background``
          inputs when calculating properties.
          """
  
          mask = self._segment_mask | self._data_mask
  
          if self._input_mask is not None:
              mask |= self._input_mask
  
          return mask